Darius is so mediocre post laning phase
I know he recieved bunch of buffs during season 8. Yet it didn't change anything about him. Seriously may be its time to consider to add him some utility instead of blatant damage buffs? My suggestion is to revert his damage buffs and add him durability on his passive Noxian Might. (40-200 AD, 10-20-30% dmg reduction at levels 6/11/16).
P.S Even if we all see him as strong lane character actually he doesnt win lane that often to make it worth picking him. You can still lose lane due to camp/clear counterplay but if you win lane. Welp. Unlucky. You do nothing outside your lane.
The only reason why he's hanging at 49% wr is
setup.